This application is based on Application No. 2000-313452 filed on Oct. 13, 2000, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a mirror support structure for an optical sensor for sensing light or radio waves or an antenna for transmitting and receiving light or radio waves, which are adapted to be mounted on a moving object such as a satellite, or which are used under severe environmental conditions such as great temperature changes.
2. Description of the Related Art
FIG. 6 illustrates one example of such a known mirror support structure. In this figure, the known mirror support structure includes a main mirror 1, an auxiliary mirror 2 disposed in a face-to-face and spaced-apart relation with respect to the main mirror 1, a main mirror support member 3 in the shape of a triangular configuration with the main mirror 1 fixedly secured thereto, an auxiliary mirror support member 4 also of a triangular configuration with the auxiliary mirror 2 fixedly secured thereto, a plurality of rods 5 connecting the respective apexes of the triangular-shaped main mirror support member 3 and the respective apexes of the triangular-shaped auxiliary mirror support member 4, a plurality of support legs 6 supporting thereon the main mirror support member 3 and the auxiliary mirror support member 4, and a base panel 7 on which the support legs 6 are fixedly mounted.
With such a mirror support structure, the main mirror support member 3 and the auxiliary mirror support member 4 are arranged on the base panel 7 in such a manner that the relative positions of the main mirror 1 and the auxiliary mirror 2 can be placed in an optimal relation with respect to each other. The respective apexes of the main mirror support member 3 and the respective apexes of the auxiliary mirror support member 4 are connected with each other by means of the respective rods 5 so as to maintain the optimal relation between the primary and auxiliary mirrors 1, 2. In addition, the support legs 6 are secured at one ends thereof to the main mirror support member 3 or the auxiliary mirror support member 4 and fixedly mounted at the other ends thereof on the base panel 7. For example, in the case of an optical sensor to be installed on a satellite, it is impossible to mount the optical sensor on the satellite with a predetermined arrangement by positioning the base panel 7 in place on the satellite.
Moreover, FIG. 7 illustrates another example of a known mirror support structure. A main mirror support member 13 formed of a quadrangular panel is directly fixed to a base panel 7, and a plurality of support legs 16 each in the form of a rod serve to connect the opposite upper corner portions of the main mirror support member 13 and the base panel 7 with each other.
With the enhanced observation performance of optical sensors or radio wave sensors, and the improved performance of antennae due to the increasing transmission capacity of communications equipment in recent years, there has been a problem that the performances of the optical or radio wave sensors or antennae are adversely affected by the displacement or deformation of the mirror support structure caused by dimensional changes or environmental variations in the mirror support structure for maintaining the relative positional relation between the main mirror 1 and the auxiliary mirror 2.
That is, with the mirror support structure shown in FIG. 6, the dimensional change (expansions or contractions) and/or distortion of a mounting surface, to which the base panel 7 is fixedly secured, due to temperature changes would alter the relative positions or angles of the plurality of support legs 6, thus changing the relation between the relative positions of the main mirror support member 3 and the auxiliary mirror support member 4. As a result, there arises a problem in that the main mirror 1 and the auxiliary mirror 2 become unable to maintain the prescribed relation between their relative positions.
Furthermore, in the case of the known example of FIG. 7, in which the support legs 16 are only connected with the main mirror support member 13 but not with the auxiliary mirror support member 4, there is no such a problem as referred to above that the relative positions of the main mirror 1 and the auxiliary mirror 2 would be caused to change due to the expansion or contraction of the base panel 7. In this case, however, there arises another problem that the main mirror support member 13 would be caused to expand and contract or distort and deform due to external forces applied thereto by the connection portions thereof with the base panel 7 and/or the plurality of support legs 16, thus giving rise to adverse influences on the main mirror 1 mounted on the main mirror support member 13.
Besides, when a sensor or antenna is to be installed on an satellite, it is necessary to achieve a mirror support structure that is light in weight and high in rigidity, in order to avoid deterioration in performance which would otherwise be caused by vibrations during movement or launching thereof through a rocket.
The present invention is intended to obviate the above-mentioned problems, and has for its object to provide a light-weight and highly rigid mirror support structure of the character as described which is capable of maintaining, even with environmental variations in the place of installation and/or deformations of a mounting surface of a base panel, the relation between the relative positions of a main mirror and an auxiliary mirror in a proper manner, and of avoiding the deformation of the primary and auxiliary mirrors which would result in deterioration of the performance.
Bearing the above object in mind, according to the present invention, there is provided a mirror support structure comprising: a first mirror and a second mirror disposed a predetermined distance apart from each other in a face-to-face relation; a first mirror support member and a second mirror support member supporting the first mirror and the second mirror, respectively; a plurality of main rods connecting the first mirror support member and the second mirror support member with each other; a plurality of auxiliary rods joined at one ends thereof to the first mirror support member or the second mirror support member and at the other ends thereof to a single connection point; a plurality of support legs for indirectly supporting the first and second mirrors at a total of three points including two points on the first mirror support member and the single connection point at which the auxiliary rods are joined together; and a base on which the support legs are fixedly mounted; wherein the support legs are composed of follower members capable of following an expansion or contraction of the base.
The above and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.